In a medical infusion line, such as a phleboclysis line, it is known to provide a device for regulating the flow rate of a liquid which is delivered by a reservoir, for example a bag, and is administered, for example intravenously, to a patient. The device is located between two conduits, namely a first conduit which departs from the reservoir and the other which leads to the patient.
Various devices of the said type are known. A known type of device comprises a body presenting three parts or portions which are connected together but are free to rotate relative to each other about a common axis of rotation. A first portion is for example connected to the first conduit (connected to the liquid reservoir), and a second portion is connected to the second conduit which leads to the patient: a third portion is disposed between the first two and has means for varying the flow rate of the liquid which is to reach the patient. These flow rate variation means comprise two recesses, namely a first recess provided in that surface of the first portion which faces the third portion and a second recess provided in that surface of the second portion which faces the third portion. A seal member is present between the various portions. The first recess is annular and is of constant depth, the second recess being in the form of a broken ring of variable depth; these are connected together by a hole provided in the third part to permanently connect the first and third recesses together. Depending on the position of this hole relative to said recesses and relative to the zones in which they are connected to the corresponding conduits, the liquid originating from the reservoir undergoes a path of greater or lesser length between the two conduit connection zones via said recesses; this results in different pressure drops in the liquid flow because of a variation in the length of the path taken within the flow regulator device with consequent modification of the liquid quantity fed to the patient, This is also aided by the variable depth of the second recess.
The known devices of the aforesaid type hence comprise a body with five elements (the three portions and the two seal members between them) which is costly to produce and assemble, is costly to stock and is of large dimensions. A device of the aforesaid type is also known having a structure in which the flow rate variation means comprise a body of the aforedescribed type, but in which the recesses are connected together by a channel provided in a cylindrical side wall. This device does not offer adequate and precise regulation of the flow rate of the liquid directed to the patient, and moreover its regulation is more difficult that that of the other aforedescribed known type of device.